var g,w,i,j,s:longint;
    e,c:longint;
    v:array [1..15000] of longint;
begin
assign(input,'energii.in'); reset(input);
assign(output,'energii.out'); rewrite(output);
 for i:=1 to 15000 do v[i]:=-1;
readln(g); readln(w);
 for i:=1 to g do begin
  readln(e,c);s:=s+e;
  for j:=w downto 1 do
   if v[j]<>-1 then
    if (v[j+e]=-1)or(v[j+e]>c+v[j]) then v[j+e]:=c+v[j];
   if (v[e]=-1) or (v[e]>c) then v[e]:=c;
 end;
j:=w;
 for i:=w to 15000 do
  if (v[i]<v[j])and(v[i]>0) then j:=i;
 if (s<w) then write(-1)
          else write(v[j]);
close(input); close(output);
end.